Land Use and Climate Change Stephanie J Houser Earth Climate Systems .
Climate Change and Earth
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Climate Change and Climate Change and EarthEarth
Mommy, what were glaciers like?
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GoalsGoals
• The Earth’s unique atmosphere?• How does what we know about natural
climate change relate to what humans can do?
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The Terrestrial PlanetsWorld Atmos.
Compsn.Surface Pressure
Ave Surface Temp.
Winds, Weather
Clouds, Hazes
Mercury He, Na, O 10-14 bar Day: 800FNight: -280F
none none
Venus 96% CO23.5% N2
90 bars 880F Slow winds, acid rain
Sulfuric acid clouds
Earth 77% N221% O2H2O
1 bar 60F Winds, hurricanes, rain, snow
H2O clouds, pollution
Moon He, Na, Ar 10-14 bar Day:260FNight: -280F
none none
Mars 95% CO22.7% N2
0.007bar -60F Winds, dust storm
H2O and CO2 clouds, dust
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Why is Earth so Different?
1. Why do we have oceans of water?• Why do we have so little carbon
dioxide?
• Why do we have so much O2 and N2?
• Why do we have a UV-absorbing stratosphere?
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Concept Test
• The Earth retained so much outgassed water relative to Venus and Mars because:a. The Earth is closer to the Sun than Mars and so was
kept warmer, whereas Venus was too hot.b. The Earth is farther from the Sun than Venus and so
didn’t lose water due to thermal escape, but Mars was too cold and it all froze.
c. Both Venus and Mars lost their water due to evaporation and then UV-dissociation (while much of Mars’ water also froze).
d. The Earth simply outgassed much more water than the other two.
e. None of the above.
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I like Rain
1. Temperature just right.2. Water vapor could rain.3. Liquid oceans didn’t completely
evaporate.4. CO2 could dissolve in oceans.
– 60x CO2 dissolved in oceans as atmosphere.
– 170,000x CO2 in carbonate rocks as atmosphere.
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N and O• Nitrogen is the third most common
product of outgassing.• Water in oceans.• Carbon dioxide in oceans/rocks.• Oxygen is from life.
– Galileo spacecraft performed experimentto see if there was life on Earth.
• Life produces oxygen: O and O2.• Oxygen produces ozone O3.• Ozone absorbs UV-rays, not present on mars or
Venus.
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Goldilocks Planet
• Delicate balance: Earth is just right.– No oceans without
greenhouse gasses.– Without oceans too
many greenhouse gasses.
– Without oceans no life.
– Without life, no ozone.
– No ozone, no life.
• How does Earth maintain this balance?
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Carbon Cycle
Tectonics are crucial!
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Nature’s Thermostat
• Carbon Cycle has negative feedback.• Increasing temperatures lead to
feedback that decreases temperatures, etc.
• Positive and negative feedbacks have nothing to do with desirability of outcome.
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Too Cool
Less Rain
Less CO2 dissolves from oceans.
More CO2 builds up in atmosphere
Increased greenhouse
Heats Up.
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Too Warm
More Rain
More CO2 dissolves from oceans.
Less CO2 builds up in atmosphere
Decreased greenhouse
Cool Down.
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Ice Ages and Cycles
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Concept Test
• Under what circumstances is thermal escape likely to be important?a. Light gases on big planets far from the Sunb. Heavy gases on big planets far from the Sunc. Light gases on small planets near the Sund. Light gases on small planets far from the Sune. Equally well on any kind of gas from any kind
of planet
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Cycles
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Human Input
• Affecting CO2 cycle.
• Moving C from ground to air at increased rate.
• No increase in rate of C from air to ground.
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Mars Today
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Positive Feedback• Fossil Fuels – Increase CO2 to
atmosphere.• Deforestation – decrease CO2 from
atmosphere• Increase CO2 – Increase greenhouse effect• Increase temp – Melting glaciers, ice
sheets, polar caps• Less ice – lower planetary albedo• Lower albedo – Earth absorbs more light• More absorption – Increasing surface
temperatures.
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Homework #18Homework #18
• Due Friday 14-Nov:• Read Hansen and other web articles.• Do: Email me a single question about global
warming of the form “But, I heard that ….”